1. Download and install Autodesk Vasari 1.1
2. Download and install IronPython 2.0.3
3. Download and install RevitPythonShell
4. Launch the Vasari.exe file for the first time.
5. After Vasari has launched… close Vasari.
Note: Vasari comes as a standalone exe file but it does create a few folders on your computer which you will need in order to get it to work with RevitPythonShell.

6. Navigate to the following directory (Windows 7): C:\Users\\AppData\Roaming\Autodesk\Vasari\Addins\TP1.1
Note: This directory is where you can place custom Add-ins. Revit 2011 add-ins that take advantage of the conceptual massing environment can be also be used with Vasari. (More info can be found at thebuildingcoder)

7. Download this revitpythonshell.addin file and place it in the TP1.1 directory.
Note: This is an XML file I made which contains a path to the RevitPythonShell.dll directory. You may need to open the file to verify the path to the assembly file is correct.

8. Launch Vasari 1.1
9. Exit the current massing editor ('Cancel Mass' in the ribbon)
10. Click on the 'Add-Ins' menu tab.
11. Viola! If you did everything correctly, you should have a RevitPythonShell menu category with "Open Python Shell" and "Configure…" buttons available.
12. Congrats! You are now ready to start scripting away in Vasari with Python.

If this post needs any corrections or clarifications, please let me know!